USB is an abbreviation for Universal Serial Bus, which is a kind of external bus standard, for standardizing connection and communication between a computer and a peripheral device. A USB data line is used for the connection and communication between the computer and the peripheral device (e.g., mobile phone), for example, for data transmission and battery charging. At present, the USB plug, which is connected to a computer side, of the USB data line available on the market, typically has a structure as shown in FIG. 1. The USB plug is provided with metal contacts (that is, functional pins for implementing USB signal transmission) on a single side only. Therefore, the USB plug with such structure may be only inserted, in a single orientation, into a USB socket on a computer side. Thus, users often need to check the orientation of the plug before inserting the plug, or need to try several times to insert the plug correctly. The usage of the USB plug with such structure is troublesome, and inconvenience is brought to users.
In order to solve problems such as inconvenient usage existing in the USB plug with such structure which can be only inserted in a single orientation, an improvement is made to the USB plug with such orientation and a double-sided USB plug is provided. In the USB plug with such structure, both front and back sides of an insulative tongue are provided with metal contacts. However, in practical application, even though both front and back sides of the USB plug are provided with metal contacts and electrical connections can be established between the metal contacts and the USB socket, the double-sided USB plug structure sometimes operates abnormally.